Novel Lanthanide Luminescent Materials Based on Complexes of 3-Hydroxypicolinic Acid and Silica Nanoparticles

New lanthanide complexes of 3-hydroxypicolinic acid (HpicOH) were prepared: [Ln(H2O)(picOH)2(μ-HpicO)]·3H2O (Ln = Eu, Tb, Er). The complexes were characterized using photoluminescence, infrared, Raman, and 1H NMR spectroscopy, and elemental analysis. The crystal structure of [Eu(H2O)(picOH)2(μ-HpicO)]·3H2O 1 was determined by X-ray diffraction. Compound 1 crystallizes in a monoclinic system with space group P21/c and cell parameters a = 9.105(13) Å, b = 18.796(25) Å, and c = 13.531(17) Å, and β = 104.86(1) deg. The 3-hydroxypicolinate ligands coordinate through both N,O- or O,O- chelation to the lanthanide ions, as shown by X-ray and spectroscopic results. Photoluminescence measurements were performed for the Eu(III) and Tb(III) complexes; the Eu(III) complex was investigated in more detail. The Eu(III) compound is highly luminescent and acts as a photoactive center in nanocomposite materials whose host matrixes are silica nanoparticles.